This invention relates generally to thrust bearings, and more particularly to a new and improved thrust bearing assembly which utilizes a novel sealing arrangement. The disclosed embodiment of the invention is directed to thrust bearing assemblies of the type used in automotive vehicles as clutch release or clutch throw-out bearings, although the invention is directed to other types of thrust bearings as well.
Generally speaking, clutch throw-out bearings provide a force-transmitting device between the foot-operated clutch pedal lever (or other clutch actuator) and other parts of the clutch assembly. Such clutch throw-out bearings are subjected to substantial forces and long periods of use, often under the rigors of adverse driving conditions. Accordingly, superior strength and durability are required to prevent premature failure of these bearings. One such clutch throw-out bearing assembly is disclosed and claimed, for example, in U.S. Pat. No. 3,909,086 issued Sept. 30, 1975.
One significant problem which arises with respect to such thrust bearings is that of maintaining adequate lubrication of the moving parts throughout a relatively long and rigorous service life of the bearing. For example, the rotation of the bearing while in service tends to cause migration of the grease or other lubricating agent outwardly of the bearing housing or "shell", thus hastening the demise of the bearing. Moreover, lack of adequate sealing invites loss of lubricant and contamination of the retained lubricant, which can also damage the bearing. Various sealing methods have been devised for such bearings and have proven generally satisfactory in operation; however, these sealing arrangements generally have required use of specially constructed seals. More specifically, the seal member is molded initially to a frusto conical configuration, such that during service the inherent resiliency of the seal will force it against the backside of the bearing. This is required to accommodate axial movement of the shell during operation as occasioned by dimensional tolerances and wear. Seals of this type, i.e. molded to a frusto conical shape, have disadvantages, in that they are expensive, and also tend to lose their resiliency during service. The present invention provides a seal member which is molded initially in a flat configuration, and is mounted in a stressed condition with only the forward edge of the base portion disposed in a mounting groove. Thus, the initially flat seal is "hoop stressed" to a frusto conical orientation, as necessary to accommodate shell movement. Further, this construction is less expensive to fabricate, and it is believed that improved service life will result.